The Avian viruses, along with the other influenza viruses, make up the virus family Orthomyxoviridae. The virus particle has an envelope with glycoprotein projections with hemagglutinating and neuraminidase activity. These two surface antigens, hemagglutinin (HA) and neuraminidase (NA), are the basis of describing the serologic identity of the influenza viruses using the letters H and N with the appropriate numbers in the virus designation e.g., H7N2. There are now 15 hemagglutinin and 9 neuraminidase antigens described among the Type A influenza viruses. The type designation (A, B, or C) is based upon the antigenic character of the M protein of the virus envelope and the nucleoprotein within the virus particle.

The incubation period is usually 3 to 7 days.

The under mentioned preventive and control measures are recommended as per the WHO guidelines:
(WHO Regional Office for the Western Pacific, Manila, 26 January 2004)

1. Cullers and transporters should be provided with appropriate personal protective equipment:

Protective clothing, preferably coveralls plus an impermeable apron or surgical gowns with long cuffed sleeves plus an impermeable apron.

Heavy duty rubber work gloves that may be disinfected.

N95 respirator masks are preferred1. Standard well-fitted surgical masks should be used if N95 respirators are not available2.

Goggles.

Rubber or polyurethane boots that can be disinfected or protective foot covers that can be discarded.

2. All persons who have been in close contact with the infected animals should wash their hands frequently with soap and water. Cullers and transporters should disinfect their hands after the operation.

3. Environmental clean up should be carried out in areas of culling, using the same protective measures as above.

4. All persons exposed to infected chickens or to farms under suspicion should be under close monitoring by local health authorities.

It is recommended that oseltamivir be readily available for the treatment of suspected H5N1 respiratory infections in cullers and farm workers involved in the mass culling3.

They should also be vaccinated with the current WHO recommended influenza vaccine to avoid simultaneous infection by human influenza and avian influenza and to minimize the possibility of a re-assortment of the virus's genes4.

Additional health monitoring of chicken cullers, others involved in the process and their family members should be carried out. These individuals should report any relevant health problems (respiratory complaints, flu-like illnesses or eye infections) to a health care facility. Persons at high risk for severe complications of influenza (e.g. immuno- compromised, over 60 years old, or with known chronic heart or lung disease) should avoid working with affected chickens.

5. Serological surveillance of exposed animal workers and veterinarians is encouraged.

6. In liaison with designated laboratories, full blood and post mortem specimens (intestinal contents, anal and oro-nasal swabs, trachea, lung, intestine, spleen, kidney, brain, liver and heart) of animals (including pigs) should be collected for investigation of new viral isolates.

References

1 US NIOSH certified N-95, European CE P2, or comparable national/regional standards applicable to the country of manufacture. Higher level particulate respirators may also be used.

2 In the control of the outbreak of avian influenza in the Netherlands in 2003, N95 or equivalent respiratory protection was used.

3 For treatment, oseltamivir phosphate (Tamiflu®): 75 mg capsule twice daily, for 5 days.

4 All concerned (persons at risk both environmentally and occupationally) should be vaccinated with the current WHO recommended influenza vaccine as soon as possible prior to anticipated risk exposure (2 weeks are required to develop preventive immunity by vaccination.). This does not specifically protect against H5N1.

Avoid close contact
Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.

Stay home when you are sick
If possible, stay home from work, school and errands when you are sick. You will help prevent others from catching your illness.

Cover your mouth and nose
Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.

Clean your hands
Washing your hands often will help protect you from germs.

Avoid touching your eyes, nose or mouth
Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose or mouth.

Confirmed instances of avian influenza viruses infecting humans since 1997 include :

1997 : In Hong Kong, avian influenza A (H5N1) infected both chickens and humans. This was the first time an avian influenza virus had ever been found to transmit directly from birds to humans. During this outbreak, 18 people were hospitalized and 6 of them died.

1999 : In Hong Kong, cases of avian influenza A (H9N2) were confirmed in 2 children. Both patients recovered, and no additional cases were confirmed. The evidence suggested that poultry was the source of infection and the main mode of transmission was from bird to human.

2003 : Two cases of avian influenza A (H5N1) infection occurred among members of a Hong Kong family that had traveled to China. One person recovered, the other died. How or where these 2 family members were infected was not determined. Another family member died of a respiratory illness in China, but no testing was done. No additional cases were reported.

2003 : Avian influenza A (H7N7) infections among poultry workers and their families were confirmed in the Netherlands during an outbreak of avian flu among poultry. More than 80 cases of H7N7 illness were reported (the symptoms were mostly confined to eye infections, with some respiratory symptoms), and 1 patient died (in a veterinarian who had visited an affected farm). There was evidence of some human-to-human transmission.

2003 : H9N2 infection was confirmed in a child in Hong Kong. The child was hospitalized but recovered.

An influenza pandemic is a global outbreak of influenza and occurs when a new influenza virus emerges, spreads, and causes disease worldwide.
There were 3 pandemics in the 20th century. All of them spread worldwide within 1 year of being detected. They are:

1918-19, "Spanish flu," [A (H1N1)], caused the highest number of known flu deaths: more than 500,000 people died in the United States, and 20 million to 50 million people may have died worldwide. Many people died within the first few days after infection and others died of complications soon after. Nearly half of those who died were young, healthy adults.

1957-58, "Asian flu," [A (H2N2)], caused about 70,000 deaths in the United States. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957.

1968-69, "Hong Kong flu," [A (H3N2)], caused approximately 34,000 deaths in the United States. This virus was first detected in Hong Kong in early 1968 and spread to the United States later that year. Type A (H3N2) viruses still circulate today.